This invention relates to an improved control method and apparatus in which the control values of the individual cylinders of a multicylinder internal combustion engine are determined independently of one another, and particularly to a control method and apparatus suitable for controlling the ignition timing of a gasoline engine of an automobile incorporating a fuel injection control device which is computerized and electronically controlled.
A spark ignition engine, especially a gasoline engine of an automobile, must satisfy a severe exhaust gas regulation and at the same time, is required to have a sufficiently high performance. In recent years, control apparatuses have come to be adopted which are of the type that receives various kinds of data representing the operating condition of the engine one after another, and according to these data, calculates specified control data for the individual cylinders, and controls the supplied fuel quantities and ignition timing of the cylinders independently of one another. An example of such a control system is disclosed in Japanese Patent Application laid-open No. JP-A-56-92330 filed by HITACHI, LTD., for instance.
Meanwhile, in the control apparatuses of this conventional type, various kinds of data representing the operating condition of the engine are entered one after another as time elapses and are updated in a regular sequence, and according to the updated data, controlled variables such as fuel injection quantity and ignition timing are calculated in a regular sequence.
The problem with the conventional control method is as follows. In a cycle (suction stroke-compression stroke combustion stroke-exhaust stroke) in a certain cylinder, if the operating condition of the engine changes between a given sampling time of data and a subsequent sampling time, the supplied fuel flow is determined according to data at the previous sampling time, and the ignition timing is determined according to data at the subsequent sampling time. This means that an ignition timing cannot be obtained which adequately corresponds to the intake air quantity of that cycle. If, for example, the engine is accelerated suddenly, knocking or misfire will result from the inadequate ignition timing. The knocking or misfire increases components of NOx and HC in the exhaust gas, and causes drivability deterioration by a change in torque and increases the fuel consumption.
Known literature about control technology of the internal combustion engine includes Japanese Patent Application laid-open No. JP-A-64-8339 filed by Fuji Heavy Industries, Ltd. on June 30, 1987 and laid open on Jan. 12, 1989; JP-A-1-125566 filed jointly by Nissan Motor Co., Ltd. and Hitachi, Ltd. on Nov. 9, 1987 and laid open on May 18, 1989; JP-A-1-125567 filed on Nov. 11, 1987 by Hitachi, Ltd. and laid-open on May 18, 1989; JP-A-1-285641 filed on May 9, 1988 by Eagle Industries Co., Ltd. on May 9, 1988 and laid open on Nov. 16, 1989; JP-A-1-121569 filed on Nov. 2, 1987 by Fuji Heavy Industries, Ltd. and laid open on May 15, 1989; U.S. Pat. No. 4,596,220 granted to Oosuga et al. on June 24, 1986; U.S. Pat. No. 4,167,923 granted to Iwase et al. on Sept. 18, 1979; and U.S. Pat. No. 4,690,122 granted to Sasakura et al. on Sept. 1, 1979.